Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, and the description reinforces this by describing a list operation with no side effects. It adds useful behavioral detail beyond annotations by specifying the exact return fields ('route IDs, short names, and descriptions') and the full-scope nature ('all routes'). No contradictions with annotations; the behavior is consistent.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is four short sentences with no filler. It leads with the core action, then return values, then usage context, then parameter source. Every sentence serves a purpose, and the structure is logical and efficient.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's simplicity (one required parameter), the presence of an output schema, and annotations that cover read-only behavior, the description addresses everything an agent needs: what it lists, what it returns, when to use it, and where to get the parameter. No critical information is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, and the parameter description in the schema already includes examples and guidance ('Use onebusaway_list_agencies to discover IDs'). The tool description repeats the same advice without adding new meaning, so it does not go beyond what the schema provides. Baseline of 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb ('List'), a resource ('routes operated by an agency'), and the returned data ('route IDs, short names, and descriptions'). It clearly distinguishes this tool from siblings like search_routes and find_routes by emphasizing the full-service enumeration scope, leaving no ambiguity about what it does.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly says 'Use to enumerate an agency's full service before searching for a specific route,' providing clear context for when to call it. It also directs the user to onebusaway_list_agencies for discovering agencyId. However, it does not explicitly name alternatives or state when NOT to use it (e.g., when you already know the route), so it stops short of a perfect 5.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.